JP2011180379A - Image forming apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an electrophotographic-type image forming apparatus, wherein image density deviation and fogging caused by a deviation in wear amount of the surface of an image carrier are suppressed. <P>SOLUTION: On the image carrier 12, solid patterns PA and PB as density patches are formed corresponding to the positions of the ends of a transfer paper corresponding to the paper size of the transfer paper, and then, the solid patterns are scraped off and cleaned up by a cleaning device. In the cleaning device, paper powder is accumulated in a position corresponding to each of the ends of the transfer paper, and the scraped-off toner of the density patch and the paper powder are sent, in a mixed state, to a toner recycling device, accordingly, the paper powder accumulated in the cleaning device can be removed, then, the deviation in wear amount of the surface of the image carrier can be suppressed. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus that forms an image using toner.

  Conventionally, an electrophotographic image forming apparatus (an image forming apparatus that forms an image using an electrophotographic process) generally collects toner remaining on a photoconductor (image carrier) after transfer, A cleaning unit is installed. The cleaning unit is composed of a rubber blade, a brush roller, and the like. The surface of the photoconductor is worn because the surface of the photoconductor is rubbed and scraped and collected.

  In such a system, the surface of the photoconductor is generally designed so that there is no problem even if it is scraped to some extent. Rather, the surface of the photoconductor is always refreshed so that the toner is transferred to the photoconductor. There is also a design concept that suppresses the occurrence of abnormal images due to thin adhesion on the surface.

  Another technique for constantly refreshing the surface of the photosensitive member is to apply a lubricant on the photosensitive member and scrape the lubricant with a cleaning device to form an image. If the technology that collects transfer residual toner, conveys it to the developing device, and uses it as recycled toner is applied, the lubricant is also mixed into the developing device together, so that the charging of the toner becomes unstable and the toner There are problems such as scattering and fogging.

  Therefore, when using a technique for improving the yield by toner recycling (improving the number of sheets that can be copied per toner replenishing container), it is more advantageous to scrape the surface of the photoconductor than to apply a lubricant. I can say that.

  However, a problem occurs when the surface of the photoconductor does not wear uniformly and the wear amount varies. That is, when the wear amount is deviated, the surface thickness of the photosensitive member becomes non-uniform, so that a charged potential deviation due to a deviation in capacitance occurs, and an image density deviation occurs. Further, in a portion where the amount of wear has increased, development (fogging) on a non-image portion due to electrostatic breakdown occurs, which is a serious problem.

  One factor of such wear amount deviation is the presence of paper dust. Paper dust is a fiber generated from transfer paper. However, as long as paper is used as transfer paper, the generation of paper dust cannot be eliminated. Therefore, in general electrophotographic image forming devices, transfer paper is transported. For example, a Mylar for scraping and collecting paper dust on a conveying roller or the like in the path is installed, or paper dust is collected together with toner remaining on the photosensitive member by a cleaning unit.

  However, paper dust tends to be generated especially at the edge of the paper, and the paper edge is basically a non-image portion and there is no toner input (toner adheres), so the paper dust is used as residual transfer toner. It is difficult to collect together. As a result, the paper dust easily collects in the cleaning unit at the position corresponding to the edge of the paper, and the paper dust staying in the cleaning unit keeps rubbing against the surface of the photoreceptor. The amount of scraping on the surface increases and wear amount deviation (film thickness deviation) occurs.

  In such a wear amount deviation (film thickness deviation) due to paper dust generated at a position corresponding to the paper edge, an image is not formed on the paper edge when the paper edge is always the same. Concentration deviation does not occur. However, when the film thickness becomes thin and fogging due to electrostatic breakdown occurs, the transfer paper edge is contaminated with toner, and the paper edge changes depending on the size of the paper used. Since the ends are not always the same, a problem of image density deviation may occur.

  To deal with such a problem, Patent Document 1 discloses that the dimension in the longitudinal direction of the image carrier (image forming main scanning direction) is longer than the maximum transfer material size in the longitudinal direction of the image carrier, and the rotational direction of the image carrier ( By forming an image pattern whose dimensions in the image forming sub-scanning direction) are shorter than the contact length between the transfer member and the image carrier, and inputting toner to the blade of the cleaning unit, the retention of paper dust is suppressed and a small amount of paper A technique is disclosed in which even if the powder stays, the friction of the paper dust is weakened by the input toner and the deterioration of the image quality due to the deviation of the wear amount of the photoconductor is prevented.

  However, in Patent Document 1, not only paper dust but also foreign matter from which additives in rubber such as a transfer roller have been removed is taken into account in almost all areas in the longitudinal direction of the image carrier. In the configuration of a general electrophotographic image forming apparatus, the generation of foreign matters is not biased to a specific position, and this is also true in the embodiment of Patent Document 1.

  Therefore, regarding the wear amount deviation of the image carrier, in Patent Document 1, since toner input other than the position corresponding to the substantial paper edge is also performed, there is a lot of useless toner input, and toner yield (toner It can be said that there is a problem such as an increase in cost due to a decrease in the number of copies that can be made per supply container.

  Japanese Patent Laid-Open No. 2004-228688 is based on the fact that an image pattern is formed on the image carrier at a position corresponding to both ends in the longitudinal direction of the developing roller end portion, and toner is consumed, so that the magnetic force at the developing roller end portion is strong. A technique for suppressing development ability deviation is disclosed. In this technique, toner is input to a specific area, but the purpose is not to reduce the deviation of the wear amount of the image carrier, so the position corresponding to the paper edge and the toner input position are not always the same, and Since the toner input position is always constant, when the paper size to be used changes, the paper edge position and the toner input position are shifted, and the effect of reducing the wear amount of the image carrier cannot be obtained.

  Patent Document 3 discloses a technique for forming an image pattern in a non-image area on a photoconductor (image carrier), forcibly discharging deteriorated toner, and suppressing deterioration in image quality due to the deteriorated toner. However, similarly to Patent Document 2, the technique disclosed in Patent Document 3 cannot always obtain the effect of reducing the wear amount of the image carrier.

  The present invention has been made in view of such a situation, and in an electrophotographic image forming apparatus, image density deviation due to wear amount deviation on the surface of an image carrier and development (fogging) of toner on a non-image portion are performed. It aims to be able to suppress.

  In order to achieve the above object, the present invention cleans toner remaining on an image carrier for carrying a latent image, and removes residual toner scraped from the image carrier by the cleaning device. In an image forming apparatus comprising a toner recycling device that collects and conveys the toner again to a developing device, transfer paper size acquisition means for acquiring the size of the transfer paper used for image formation in the main scanning image direction, and the transfer A toner image having a predetermined image pattern is acquired on the image carrier at a predetermined timing at a position corresponding to an end portion in the image forming main scanning direction of the transfer paper used for image formation acquired by the paper size acquisition unit. Control means for forming the toner image, and the toner image is not transferred onto the transfer paper, and the toner image is scraped off from the image carrier by the cleaning device. It is obtained by way.

Further, it is preferable to further comprise density detecting means for detecting the density of the toner image and means for adjusting the density of the toner used for developing the latent image according to the density detected by the density detecting means.
The predetermined timing may be when a continuous image forming operation without changing the transfer paper size is completed.
In addition, when a certain number of image forming operations are completed during continuous image forming operations, the image forming operation is temporarily interrupted, and the end of the transfer paper corresponding to the transfer paper size in the interrupted image forming operation. The toner image may be formed at a position on the image carrier corresponding to the portion.

  According to the image forming apparatus of the present invention as described above, it is possible to suppress the image density deviation caused by the wear amount deviation on the surface of the image carrier and the development (fogging) of the toner on the non-image portion.

1 is a schematic configuration diagram showing an outline of an overall schematic configuration of an internal mechanism of an image forming apparatus (laser copying machine) according to a first embodiment of the present invention; FIG. 2 is an enlarged schematic configuration diagram illustrating an enlarged image forming mechanism of the image forming apparatus of FIG. 1. 2 is a block diagram illustrating an example of a control system of the image forming apparatus. FIG. In the first embodiment of the present invention, the start position and end position in the axial direction of the image carrier 12 of solid patterns PA and PB, which are density patches formed on the image carrier 12 according to the transfer paper size, are shown. It is a table. 3 is a schematic configuration diagram illustrating an example of solid patterns PA and PB formed on the image carrier 12. FIG. With respect to the conventional apparatus that does not input toner at a position corresponding to the edge of the paper and the first embodiment of the present invention, 100 sheets of a general office document with an image area ratio of 6% using A4 size transfer paper. It is a graph showing the result (actual measurement value) which compared the film thickness of the image carrier 12 when printing operation is repeated and 2.5 million sheets are printed. 99 sheets of general office document with an image area ratio of 6% are printed using A5 size printing paper, and one sheet of general office document with an image area ratio of 6% is printed immediately after using A4 size printing paper. 6 is a graph showing a result (actual measurement value) of comparing the film thicknesses of the image carrier 12 between the first example and the second example when 2.5 million sheets are repeatedly printed as a set of printing operations. . The operation of printing 10,000 sheets of a general office document with an image area ratio of 6% using A4 size printing paper is repeated in the second and second embodiments when 2.5 million sheets are printed. 6 is a graph showing a result (actual measurement value) of comparing the film thicknesses of the image carrier 12. FIG. 10 is a schematic configuration diagram for explaining the position of a reflection density sensor SS ′ provided in the vicinity of an image carrier 12 and solid patterns PC and PD in a fourth embodiment of the present invention. In the fourth embodiment of the present invention, a solid pattern PC or PD, which is a density patch formed on the image carrier 12 according to the transfer paper size, a table indicating the start position and end position in the axial direction of the image carrier 12. It is. An operation of printing 10 sheets of a general office document with an image area ratio of 6% using A4 size printing paper for a conventional apparatus that does not input toner at a position corresponding to the paper edge and the fourth embodiment. Is a graph showing the result (actual measurement value) of comparing the film thickness of the image carrier 12 when 2.5 million sheets are printed repeatedly. Nine general office documents with an image area ratio of 6% are printed using A5 size printing paper, and one general office document with an image area ratio of 6% is printed immediately after using A4 size printing paper. FIG. 5 is a graph showing results (actual measurement values) obtained by comparing the film thicknesses of the image carrier 12 between the fourth example and the fifth example when the printing operation is repeated as one set and 2.5 million sheets are printed. is there. The operation of printing 10,000 sheets of a general office document with an image area ratio of 6% using A4 size printing paper is repeated between 2.5 and 5 million sheets, and the fifth and sixth embodiments are the same. 6 is a graph showing a result (actual measurement value) of comparing film thicknesses of an image carrier 12.

Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings.
[First embodiment]
FIG. 1 is a schematic diagram showing the outline of the overall schematic configuration of the internal mechanism of the image forming apparatus (laser copying machine) according to the first embodiment of the present invention. FIG. 2 is an enlarged schematic configuration diagram illustrating the image forming mechanism of the image forming apparatus of FIG. 1 in an enlarged manner.

  In FIG. 1, reference numeral 10 denotes an image forming apparatus main body. An image carrier 12 made of a drum-shaped photoconductor is provided in the image forming apparatus main body 10. Around the image carrier 12, a charging device 13, a developing device 14, a transfer / conveyance device 15, a cleaning device 16, a static elimination device 17, and the like are arranged. And the laser writing device 18 is provided in those upper parts.

The laser writing device 18 includes a light source 20 such as a laser diode, a scanning rotary polygon mirror 21, a polygon motor 22 that rotationally drives the rotary polygon mirror 21, a scanning optical system 23 such as an fθ lens, and the like. In this case, the width is 307 mm.
A fixing device 25 is disposed on the left side of the cleaning device 16 in the drawing. The fixing device 25 includes a fixing roller 26 incorporating a heater, and a pressure roller 27 that presses against the fixing roller 26 from below.

  A document reading device 30 is provided in the upper part of the apparatus main body 10. The document reading device 30 is provided with a light source 31, a plurality of mirrors 32, an imaging lens 33, an image sensor 34 such as a CCD. Further, a transfer paper stacking tray 70 is provided at the lower part of the apparatus main body 10 to feed transfer paper. In this case, the maximum paper feed width is 330.2 mm, and in the vicinity of the image carrier 12. A registration roller 48 is provided.

  The developing device 14 includes a developing tank 50 and a developing hopper 60 as shown in FIG. In the developing tank 50, a first developing roller 51, a second developing roller 52, a paddle wheel 53, a stirring roller 54, a conveying screw 55, a separator 56, a doctor blade 57, a toner concentration sensor 58 and the like are provided in a developing case 59. In the developing case 59, a two-component developer composed of carrier and toner is stored.

  In the developing hopper 60, a gear-shaped toner replenishing member 61, a replenishment regulating plate 62, an agitator 63, and the like are provided. The developing hopper 60 stores toner. In the developing device 14, the two-component developer in the developing case 59 is stirred and frictionally charged by the rotation of the stirring roller 54, and is flipped up by the rotation of the paddle wheel 53. The first developing roller 51 and the second developing roller 52 are attracted by the magnet in the roller 52.

  The developer adsorbed on the first developing roller 51 and the second developing roller 52 is transported by the developing sleeves on the outer periphery of the first developing roller 51 and the second developing roller 52 and scraped off by the doctor blade 57. The electrostatic latent image on the image carrier 12 is developed by being attached to the image carrier 12 by the action of the developing bias voltage applied to the developing sleeve.

  In this embodiment, bias voltages are applied to the developing sleeve and the developing case 59 (made of aluminum) from individual power packs (power supply devices). A developing bias voltage of −650 V is applied to the developing sleeve, and an arbitrarily determined bias voltage is applied to the developing case 59 (hereinafter referred to as a casing bias). The developable area is determined by the length in the longitudinal direction of the developing sleeve, and is 310 mm in this case. Further, the linear velocity of the developing sleeve of this embodiment is 700 mm / sec.

  In the developing device 14, when the toner adheres to the image carrier 12 and is consumed, the ratio (toner concentration) decreases. Therefore, when the toner concentration in the developer becomes equal to or lower than a predetermined value with respect to the target value of the toner concentration, the agitator 63 is rotated to stir the toner and transport the toner to the toner supply member 61. The toner supply member 61 is rotated. Then, the replenishment regulating plate 62 is swung to replenish toner from the developing hopper 60 into the developing tank 50 to maintain the toner concentration in the developer.

  Here, the toner concentration in the developer is measured by a toner concentration sensor 58 attached to the developing case 59. This toner concentration sensor 58 detects the toner concentration by detecting the change in the magnetic permeability of the developer in a certain volume near the sensor using the inductance of the coil.

In this embodiment, the toner density calibration is performed as follows every time the number of printed sheets of the image forming apparatus reaches a predetermined number of printed sheets.
That is, the reference density patch latent image is written on the image carrier 12 with the laser beam of the laser writing device 18, a developing bias voltage corresponding to the reference density patch is applied to the developing sleeve, and a predetermined developing potential voltage (for example, 280V) is applied. A reference density toner image (hereinafter, density patch) is developed.

  Then, the reflection density of the density patch is detected by a reflection density sensor (described later) provided in the vicinity of the image carrier 12, and the toner in the developing hopper 60 is replenished so that the reflection density falls within a certain range.

  Here, in the developing device 14, a two-component developer including a toner having a weight average particle diameter of 5 to 10 μm and a toner having a weight average particle diameter of 6 μm or less and a toner containing 60 to 80% by number of 5 μm or less is used. . The toner may be composed of a resin component and a colorant, and may further include a wax component and inorganic fine particles. Further, the method for producing the toner is not particularly limited, and either a pulverization method or a polymerization method can be used.

  As the resin component, all conventionally known resins can be used, and examples thereof include the following. Styrene, poly-α-still styrene, styrene-chlorostyrene copolymer, styrene-propylene copolymer, styrene-butadiene copolymer, styrene-vinyl chloride copolymer, styrene-vinyl acetate copolymer, styrene-malein Styrene resins such as acid copolymers, styrene-acrylic acid ester copolymers, styrene-methacrylic acid ester copolymers, styrene-α-chloroacrylic acid methyl copolymers, styrene-acrylonitrile-acrylic acid ester copolymers ( Styrene or styrene-substituted monopolymer or copolymer), polyester resin, epoxy resin, vinyl chloride resin, rosin-modified maleic acid resin, phenol resin, polyethylene resin, polyester resin, polypropylene resin, petroleum resin, polyurethane resin, Ketone resin, ethylene N-ethyl acrylate copolymer, xylene resin, polyvinyl butyrate resin and the like. Moreover, although single use is also possible, you may use together two types.

  Examples of known colorants include carbon black, lamp black, iron black, ultramarine, nigrosine dye, aniline blue, calco oil blue, oil black, azo oil black, and the like. Any of these colorants may be used. Known wax components include carnauba wax, rice wax, and synthetic ester wax, and any of these wax components may be used in this embodiment. As the inorganic fine particles, known ones include silica, titanium oxide fine powder, and the like, and any of these inorganic fine particles may be used as a material applied to this embodiment.

Incidentally, as described above, the toner attached to the image carrier 12 is electrostatically transferred onto the transfer paper by the transfer / conveyance device 15. However, about 10% of the toner remains on the image carrier 12 without being transferred to the transfer paper. Residual toner is scraped off from the image carrier 12 by a brush roller 16 a and a cleaning blade 16 b provided in the cleaning device 16.
The toner scraped off from the image carrier 12 by the cleaning device 16 enters the recovery tank 16 c of the cleaning device 16. Then, the toner is conveyed to one side of the cleaning device 16 by the recovery screw 16d, discharged from a discharge port (not shown), led to a toner recycling device (not shown), and circulated into the developing hopper 60 by the toner recycling device. Used for development.

FIG. 3 is a block diagram illustrating an example of a control system of the image forming apparatus.
In FIG. 3, the control system of the image forming apparatus includes an operation device 81, a display device 82, an auxiliary storage device 83, a memory device 84, a main control unit 85, an image forming unit 86, a document reading unit 87, a paper feeding unit 88, In addition, a bus B for exchanging data between these devices is provided.

  The operation device 81 has various switches and operation keys for the user to operate the image forming apparatus, and the display device 82 is for displaying the operation state of the image forming apparatus and various messages. And a liquid crystal display device and various light emitting elements. The operation device 81 and the display device 82 constitute a UI (user interface) for the user to operate the image forming apparatus.

  The auxiliary storage device 83 is a non-volatile storage device for the CPU of the main control unit 85 to store data, and the memory device 84 constitutes a work area or the like such as the CPU of the main control unit 85. The data is saved. The main control unit 85 is composed of a computer system including a CPU, and controls the operation of each unit of the image forming apparatus.

  The image forming unit 86 appropriately controls the image carrier 12, the charging device 13, the developing device 14, the transfer / conveyance device 15, the cleaning device 16, the charge eliminating device 17, and the laser writing device 18, and transfers it by an electrophotographic process. An image is formed on paper.

  The document reading unit 87 is for reading an image of a document using the document reading device 30, and the paper feeding unit 88 separates and conveys the transfer sheets loaded on the transfer sheet stacking tray 70 one by one, This is for controlling the operation of feeding into the main body 10.

FIG. 4 shows the start position and end of the solid patterns PA and PB, which are density patches formed on the image carrier 12 according to the transfer paper size, in the axial direction of the image carrier 12 in the first embodiment of the present invention. It is a table | surface which shows each position. FIG. 5 shows an example of the solid patterns PA and PB formed on the image carrier 12.
As described above, the image carrier that forms the solid patterns PA and PB so as to form the solid patterns PA and PB at the position corresponding to the edge of the transfer paper corresponding to each paper size (area including the edge). Twelve axial positions are set.

  In the first embodiment of the present invention, a transfer paper stacking tray 70 shown in FIG. 1 is provided with a general transfer paper size detection sensor (not shown). Input from the paper unit 88 to the main control unit 85.

  The main control unit 85 uses the image forming unit 86 to place the solid patterns PA and PB having the circumferential length of 80 mm on the image carrier 12 at the positions shown in the table of FIG. 4 according to the paper size of the transfer paper as shown in FIG. Are formed corresponding to the paper size of the transfer paper of the final print page at the end of the printing operation when the cumulative number of sheets passed is 100 or more.

  Here, the reference position of the dimension in the axial direction of the image carrier 12 is set at the end on the front side of the main body at the left end of the figure. Further, the circumferential length of the image carrier 12 of the solid patterns PA and PB is such that the amount of toner scraped by the cleaning device 16 is recycled together with the scraped toner with the paper dust accumulated inside the cleaning device 16. The dimensions are set so that they can be discharged into the apparatus.

  Here, symbol SS in FIG. 5 indicates a reflection density sensor used in the above-described calibration of the toner density. Therefore, at the time of calibration of the toner density, a density patch PP having a shape as indicated by a broken line in the figure is formed at a position where the reflection density sensor SS can detect, and the density of the density patch PP is changed to the reflection density. Detected by sensor SS.

  Regarding the toner density calibration, the main control unit 85 performs the toner density calibration as described above by the image forming unit 86 every time the number of printed sheets of the image forming apparatus reaches a predetermined number of printed sheets.

  FIG. 5 shows solid patterns PA and PB formed at the toner input pattern positions when A4 size paper is detected. Further, the image forming unit 86 forms the solid patterns PA and PB at the end of the printing operation and before the image carrier 12 stops, and then stops the image carrier 12 to generate downtime. Is reduced as much as possible.

  Further, since the purpose is to input the solid patterns PA and PB to the cleaning device 16, the image forming unit 86 does not transfer the solid patterns PA and PB when the solid pattern is formed. Is separated from the image carrier 12 by a solenoid (not shown).

  Further, after the formation of the solid patterns PA and PB, the main control unit 85 is configured to reset the accumulated sheet passing number and count up again from the first sheet. Thereby, as shown in FIG. 6, the film thickness deviation of the image carrier 12 can be suppressed.

  FIG. 6 shows a general office with an image area ratio of 6% using A4 size transfer paper for the conventional apparatus that does not input toner at a position corresponding to the edge of the paper and the first embodiment of the present invention. This is a result (actual measurement value) of comparing the film thicknesses of the image carrier 12 when the operation of printing 100 documents is repeated 2.5 million sheets. A solid line shows a graph corresponding to the first embodiment, and a broken line shows a graph of the conventional apparatus.

  During the 2.5 million sheet printing operation, in the case of the first embodiment, the main control unit 85 inputs the sheet size of the transfer sheet on the transfer sheet stacking tray 70 one by one from the sheet feeding unit 88, while An image is formed on transfer paper by the forming unit 86, and the total number of sheets is sequentially counted up from 1.

  When the operation of printing 100 sheets, which is one set of printing, is finished, the main control unit 85 resets the total number of sheets to 0 and the paper size of the 100th transfer sheet input from the sheet feeding unit 88. Is designated to the image forming unit 86, and a solid patch PA, PB density patch is formed on the image carrier 12, and the cleaning device 16 is instructed to perform the scraping operation.

  As a result, the image forming unit 86 writes the patch latent image for the density patch of the solid patterns PA and PB corresponding to the paper size designated by the main control unit 85 to the image carrier 12 with the laser light of the laser writing device 18. Then, a developing bias voltage corresponding to the density patch is applied to the developing sleeve, the density patch is developed with a predetermined development potential voltage (for example, 280 V), and density patches of solid patterns PA and PB are formed on the image carrier 12.

  Further, the image forming unit 86 separates the transfer / conveyance device 15 from the image carrier 12 by a solenoid (not shown) so as not to perform the transfer of the solid patterns PA and PB when the solid patterns PA and PB are formed. The density patches of the solid patterns PA and PB formed on the image carrier 12 are scraped off by the brush roller 16a and the cleaning blade 16b of the apparatus 16.

  The toner scraped off from the image carrier 12 by the brush roller 16a and the cleaning blade 16b of the cleaning device 16 is mixed with the paper dust accumulated in the cleaning device 16 corresponding to the end of the transfer paper in the main scanning direction, The toner and paper dust are collected and sent to a toner recycling device. Thereby, the paper dust accumulated in the cleaning device 16 is removed.

  In this way, when printing 2.5 million sheets, in the first embodiment, the paper dust accumulated in the cleaning device 16 is removed every time 100 sheets are printed. On the other hand, since the conventional apparatus does not perform the operation as in the first embodiment, the paper dust accumulated in the cleaning apparatus 16 is not removed.

  Therefore, as shown in FIG. 6, in the conventional apparatus, electrostatic breakdown occurs at the portion where the film thickness is reduced due to the paper dust accumulated in the cleaning device 16, and development (fogging) on the non-image portion is caused. However, since the film thickness deviation can be suppressed in the first embodiment, the fogging stain does not occur.

  Further, in the first embodiment, the paper size is detected by the paper size detection sensor provided in the transfer paper stacking tray 70, but this does not limit the paper size detection method. A paper size may be detected by providing a sensor such as a light emitting element in the paper conveyance path. In addition, when using a peripheral device with an additional transfer paper stacking tray as an option, it is also possible to detect the paper size with the paper size detection sensor provided on the additional transfer paper stacking tray, and transfer from the manual feed tray. Even when paper is fed, it can be handled by providing a paper size detection sensor in the manual paper feed unit.

However, since it can be said that there is almost no application of feeding a large amount from the manual feed tray, the paper size detection means can be omitted from the hand tray. Further, the sizes and formation positions of the solid patterns PA and PB are not limited to those described above, and the axial direction of the image carrier 12 of the detected transfer paper size (that is, the main scanning direction during image formation). ) As long as toner can be input to the paper edge.
Also, for example, the paper size of the transfer paper set corresponding to the tray is used as it is, or the paper size of the transfer paper input by the user is used as it is. It is also possible to adopt a method for recognizing.

  In the first embodiment, every time 100 printing operations are performed continuously, the solid pattern PA and PB forming operation and the cleaning operation are performed. However, the solid pattern PA and PB forming operation is performed. The number of continuous printing operations (the number of continuous printing) for performing the cleaning operation and the cleaning operation is not limited thereto.

[Second Embodiment]
In the second embodiment of the present invention, in the first embodiment described above, the formation timing of the solid patterns PA and PB is after the end of one continuous printing in which the paper size does not change. Since the premise apparatus configuration in the second embodiment is the same as that of the first embodiment described above, description thereof is omitted.

  As a result, since the solid patterns PA and PB can be formed for each minimum printing operation in which the paper size does not change, the film thickness deviation of the image carrier 12 can be suppressed even when the paper size changes frequently.

  FIG. 7 shows a typical office document with an image area ratio of 6% printed using 99 sheets of an A5 size printing paper and immediately after using an A4 size printing paper with an image area ratio of 6%. The result of comparing the film thicknesses of the image carrier 12 in the first and second embodiments (actual measurement values) when 2.5 million sheets are printed repeatedly as an operation of printing one document. is there. A solid line indicates a graph corresponding to the second embodiment, and a broken line indicates a graph corresponding to the first embodiment.

  In this case, in the first embodiment, the above-described operation is performed every time 100 sheets are printed. That is, in the case of the first embodiment, the main controller 85 designates A4 which is the paper size of the 100th transfer sheet when the 100-sheet printing operation is completed, and A command is given to form density patches of solid patterns PA and PB on the image carrier 12 and perform a scraping operation by the cleaning device 16.

  Therefore, in the first embodiment, the paper size detected at the timing of the toner input when the solid pattern PA, PB is formed every 100 sheets and the toner is input is A4 size. Since the paper size used in the majority of printing is different from the A5 size, the toner input position by the solid patterns PA and PB is not appropriate, and as a result, electrostatic breakdown occurs at the point where the film thickness is reduced. As a result, development (fogging) on the non-image area has occurred. This state is shown in the graph shown by the broken line in FIG.

  On the other hand, in the second embodiment, the main control unit 85 forms the image on the transfer paper by the image forming unit 86 while inputting the paper size of the transfer paper on the transfer paper stacking tray 70 one by one from the paper supply unit 88. To do. When 99 sheets of printing on the A5 transfer sheet are finished, the paper size input from the paper supply unit 88 in the next printing operation is A4, and the change of the paper size is recognized at that time.

  Upon recognizing the change in the paper size, the main control unit 85 designates A5 which is the paper size of the 99th transfer sheet at that time, that is, after the 99 sheets of printing on the A5 transfer sheet are finished. Then, the image forming unit 86 is instructed to form the density patches of the solid patterns PA and PB on the image carrier 12 and perform the scraping operation by the cleaning device 16. Note that the formation of the solid patterns PA and PB performed by the image forming unit 86 and the cleaning operation by the cleaning device 16 are the same as those in the first embodiment described above, and thus the description thereof is omitted.

  Next, when the main control unit 85 performs the subsequent printing operation and finishes the printing operation for the A4 transfer paper of the first page, the paper size of the transfer paper of the next page input from the paper supply unit 88 is A5. Since there is, the change in the paper size is recognized again.

  When the main control unit 85 recognizes the change in the paper size, the main control unit 85 ends the printing of the A4 transfer paper at that time, that is, after the main control unit 85 finishes printing the first transfer paper. Designating A4 as the size, the image forming unit 86 is instructed to form density patches of solid patterns PA and PB on the image carrier 12 and to perform the scraping operation by the cleaning device 16.

  In this manner, in the second embodiment, whenever the paper size of the transfer paper is changed, the density patch is formed and cleaned by the image forming unit 86 in accordance with the paper size of the transfer paper. Paper dust accumulated in the cleaning device 16 can be appropriately removed and collected. For this reason, since the film thickness deviation can be suppressed, fogging stains did not occur. This situation is shown in the graph shown by the solid line in FIG.

  Although such an operation mode is an extreme operation mode, in the first embodiment, when the paper type frequently fluctuates, there is a possibility that the toner may be input at an inappropriate position. Then, the problem is solved.

[Third embodiment]
In the third embodiment of the present invention, in the second embodiment described above, when the continuous printing operation continues continuously for a predetermined number of prints (for example, 100 prints) or more, the printing operation is performed after the 100th printing is completed. The solid prints PA and PB are formed and stopped, and then the continuous printing operation is resumed. Note that the premise of the apparatus configuration in the third embodiment is the same as that in the first embodiment, and the description thereof will be omitted.

  By doing so, in the third embodiment, the continuous printing operation on the transfer paper of the same paper size continues for a long time, so that the solid patterns PA and PB cannot be input. The film thickness deviation caused by the paper dust staying at the end position is suppressed.

  That is, in the second embodiment, the main control unit 85 forms the solid patterns PA and PB when the paper size of the transfer paper is changed, and continues the printing operation when the paper size is not changed. As a result, the continuous printing operation on the transfer paper of the same paper size continues for a long time, so that the solid patterns PA and PB cannot be input, and the paper dust stays at the paper edge position of the transfer paper in the cleaning device 16. This causes a film thickness deviation.

  On the other hand, in the third embodiment, the main controller 85 forms solid patterns PA and PB when the paper size of the transfer paper is changed, and 100 continuous printing operations without changing the paper size. In the case of continuous printing, since the printing operation is interrupted and the solid patterns PA and PB are formed after the printing of the 100th print is completed, the continuous printing on the transfer paper of the same paper size that occurs in the second embodiment. It is possible to avoid a situation in which the solid patterns PA and PB cannot be input due to the operation being continued for a long time, and it is possible to suppress a film thickness deviation caused by paper dust staying at the paper edge position of the transfer paper in the cleaning device 16.

The operation of the third embodiment at this time will be described.
The main control unit 85 causes the image forming unit 86 to form an image on the transfer paper while inputting the paper size of the transfer paper on the transfer paper stacking tray 70 one by one from the paper supply unit 88, and the total number of paper sheets is determined. Count up sequentially from 1. At the same time, it is also monitored that the paper size of the transfer paper input from the paper supply unit 88 is changed.

Here, when the value of the total sheet count reaches 100 without changing the paper size of the transfer sheet, the main control unit 85 interrupts the printing operation, resets the total sheet count to 0, and feeds paper. An operation in which density patches of solid patterns PA and PB are formed on the image carrier 12 with the paper size of the 100th transfer paper input from the unit 88 designated in the image forming unit 86 and scraped by the cleaning device 16 To do. The solid pattern PA, PB forming operation performed by the image forming unit 86 and the cleaning operation by the cleaning device 16 are the same as those in the first embodiment, and the description thereof is omitted.
When the solid pattern PA and PB forming operation and the cleaning operation are finished, the main control unit 85 resumes the interrupted printing operation.

  FIG. 8 shows the second embodiment and the third embodiment when the operation of printing 10,000 sheets of a general office document with an image area ratio of 6% using A4 size printing paper is repeated and 2.5 million sheets are printed. The result (actual measurement value) of comparing the film thickness of the image carrier 12 with the example is shown. A solid line indicates a graph corresponding to the third embodiment, and a broken line indicates a graph corresponding to the second embodiment.

  In this case, in the second embodiment, the main control unit 85 does not change the paper size, so that the solid patterns PA and PB are not formed in the printing operation of 2.5 million sheets, whereas the third embodiment is performed. In the example, the main control unit 85 interrupts the printing operation every 100th print, and the image forming unit 86 performs the formation operation of the solid patterns PA and PB corresponding to the paper size of the transfer paper and the cleaning operation.

  As described above, in the second embodiment, since there are few opportunities to form the solid patterns PA and PB (in this case, the solid patterns PA and PB are not formed), a film thickness deviation occurs. In the example, the printing operation is interrupted every 100th print, and the solid pattern PA, PB forming operation and cleaning operation are performed by the image forming unit 86, so that the film thickness deviation can be suppressed. For this reason, in the second embodiment, electrostatic breakdown occurs at the portion where the film thickness is reduced and development (fogging) occurs in the non-image area. In the third embodiment, the film thickness deviation is suppressed. As a result, fogging did not occur.

[Fourth embodiment]
The difference between the fourth embodiment and the first embodiment of the present invention is that, as shown in FIG. 9, the position of the reflection density sensor SS ′ provided in the vicinity of the image carrier 12 is the main body of the two density patches. The point where the solid pattern PC on the near side (left side in FIG. 9) is provided at a detectable position and the two density patches formed on the image carrier 12 are different from the solid patterns PA and PB of the first embodiment. This is a point where solid patterns PC and PD are used. In the fourth embodiment, the other preconditions are the same as those in the first embodiment, and a description thereof will be omitted.

  Here, the shapes of the solid patterns PC and PD are such that the axial dimension of the image carrier 12 is set according to the table shown in FIG. 10 and the circumferential length of the image carrier 12 is 120 mm. is there. The solid pattern PC is provided on the front side of the main body (left side in FIG. 9), and the solid pattern PD is provided on the back side of the main body (right side in FIG. 9).

  In the fourth embodiment, the density patch is formed at the end of the printing operation when the cumulative number of sheets passed exceeds 10, and the reflection of the solid pattern PC formed on the front side of the main body of the density patch. The density is detected by the reflection density sensor SS ′, and the toner in the developing hopper 60 is replenished so that the reflection density falls within a certain range. That is, the operation of forming and cleaning the solid patterns PC and PD is used as the calibration of the toner density.

  Here, FIG. 9 shows the position of the toner input pattern (solid pattern PC, PD) when A4 size paper is detected. Also in the fourth embodiment, as in the first embodiment, the density patch (solid pattern PC, PD) is formed at the end of the printing operation and before the image carrier 12 stops. Then, the occurrence of downtime is minimized by stopping the image carrier 12 thereafter. Further, since the purpose is to input the toner of the density patch to the cleaning device 16, the transfer / conveyance device 15 is moved from the image carrier 12 to a solenoid (not shown) so as not to transfer the density patch when forming the density patch. ). In addition, after the density patch is formed, the cumulative number of sheets passed is reset and counted up again from the first sheet.

  Thereby, as shown in FIG. 11, the film thickness deviation of the image carrier 12 can be suppressed. FIG. 11 shows a general office document with an image area ratio of 6% using A4 size printing paper for the conventional apparatus that does not input toner at a position corresponding to the edge of the paper and the fourth embodiment. This is a result (actual measurement value) of comparing the film thicknesses of the image carrier 12 when 2.5 sheets are printed by repeating the operation of printing 10 sheets. A solid line shows a graph corresponding to the fourth embodiment, and a broken line shows a graph corresponding to the conventional apparatus.

  In the case of the fourth embodiment, during the 2.5 million sheet printing operation, the main control unit 85 inputs the sheet size of the transfer sheet on the transfer sheet stacking tray 70 one by one from the sheet feeding unit 88, while An image is formed on transfer paper by the forming unit 86, and the total number of sheets is sequentially counted up from 1.

  When the operation of printing 10 sheets, which is one set of printing, is finished, the main control unit 85 resets the total number of sheets to 0, and the paper size of the 10th transfer sheet input from the sheet feeding unit 88. Is designated to the image forming unit 86, and a solid pattern PC, PD density patch is formed on the image carrier 12, and the cleaning device 16 performs a scraping operation.

  As a result, the image forming unit 86 writes the patch latent image for the density patch of the solid pattern PC, PD corresponding to the paper size designated by the main control unit 85 to the image carrier 12 with the laser light of the laser writing device 18. Then, a developing bias voltage corresponding to the density patch is applied to the developing sleeve, the density patch is developed with a predetermined development potential voltage (for example, 280 V), and the density patches of the solid patterns PC and PD are formed on the image carrier 12.

  Further, the image forming unit 86 detects the reflection density of the solid pattern PC formed on the front side of the main body of the density patch by the reflection density sensor SS ′, and adjusts the reflection density in the developing hopper 60 so that the reflection density falls within a certain range. Add toner.

  Then, the image forming unit 86 separates the transfer / conveyance device 15 from the image carrier 12 by a solenoid (not shown) so as not to transfer the solid patterns PC and PD when the solid patterns PC and PD are formed. The density patches of the solid patterns PC and PD formed on the image carrier 12 are scraped off by the brush roller 16a and the cleaning blade 16b of the apparatus 16.

  The toner scraped off from the image carrier 12 by the brush roller 16a and the cleaning blade 16b of the cleaning device 16 is mixed with the paper dust accumulated in the cleaning device 16 corresponding to the end of the transfer paper in the main scanning direction. The toner and paper dust are collected and sent to a toner recycling device. Thereby, the paper dust accumulated in the cleaning device 16 is removed.

  In this way, when printing 2.5 million sheets, in the fourth embodiment, paper dust accumulated in the cleaning device 16 is removed every time 10 sheets are printed. On the other hand, since the conventional apparatus does not perform the operation as in the fourth embodiment, the paper dust accumulated in the cleaning apparatus 16 is not removed.

  For this reason, as shown in FIG. 11, in the conventional apparatus, electrostatic breakdown occurs at the portion where the film thickness is reduced due to the paper dust accumulated in the cleaning device 16, and development (fogging) on the non-image portion is caused. Although it occurred, in the fourth example, since the film thickness deviation could be suppressed, the fogging stain did not occur.

  In the fourth embodiment, the solid pattern PC and PD forming operation and the cleaning operation are performed every time 10 printing operations are performed continuously. However, the solid pattern PC and PD forming operation is performed. The number of continuous printing operations (the number of continuous printing) for performing the cleaning operation and the cleaning operation is not limited thereto. Further, the size and formation position of the density patch (solid pattern PC, PD) are not limited. Toner can be input to the paper edge of the paper size to be detected, and the reflection density of the density patch is detected to determine the toner density. It suffices if the target image density can be adjusted (toner density calibration).

[Fifth embodiment]
In the fifth embodiment of the present invention, in the above-described fourth embodiment, the timing of density patch formation is after the end of one continuous printing in which the paper size does not change. As a result, a density patch can be formed for each printing operation in the minimum unit in which the paper size does not change. Therefore, even when the paper size changes frequently, the film thickness deviation of the image carrier 12 can be suppressed as shown in FIG. it can.

  The operation of the fifth embodiment is the same as that of the second embodiment described above except that the solid pattern formed on the image carrier 12 is changed to the solid patterns PC and PD, and that the toner density is calibrated. Since is the same, description thereof is omitted.

  Here, FIG. 12 shows that a general office document with an image area ratio of 6% is printed using A5 size printing paper, and an ordinary image with an image area ratio of 6% is printed immediately after using A4 size printing paper. The result of comparing the film thickness of the image carrier 12 in the fourth and fifth embodiments when printing 2.5 million sheets is repeated as an operation of printing one typical office document as one set ( Measured value). A solid line indicates a graph corresponding to the fifth embodiment, and a broken line indicates a graph corresponding to the fourth embodiment.

  In the fourth embodiment, since the paper size detected at the toner input timing is different from the paper size actually used in most printing, the toner input position is not appropriate, and as a result, the film thickness becomes thin. However, in the fifth embodiment, since the film thickness deviation can be suppressed, the fogging stain is generated. There wasn't. Although it is an extreme mode, in the fourth embodiment, when the paper type frequently fluctuates, there is a possibility that the toner may be input at an inappropriate position, whereas in the fifth embodiment, the problem is solved. .

[Sixth embodiment]
In the sixth embodiment of the present invention, in the fifth embodiment described above, when the continuous printing operation continues continuously for 100 prints or more, the density patch is formed after the printing of the 100th print is completed. The continuous printing operation is resumed later. This not only suppresses film thickness deviation due to paper dust staying at the edge of the paper due to the fact that the continuous patch operation continues for a long time and toner input to the density patch is not possible, and also stabilizes the image density with the density patch. is doing.

  The operation of the sixth embodiment is the same as the third embodiment except that the solid pattern formed on the image carrier 12 is changed to the solid patterns PC and PD, and that the toner density is calibrated. Since is the same, description thereof is omitted.

  In FIG. 13, the operation of printing 10,000 sheets of a general office document with an image area ratio of 6% using A4 size printing paper is repeated, and the fifth and sixth embodiments in the case where 2.5 million sheets are printed. The result (actual measurement value) of comparing the film thickness of the image carrier 12 with the example is shown. A solid line indicates a graph corresponding to the sixth embodiment, and a broken line indicates a graph corresponding to the fifth embodiment.

As described above, in the fifth embodiment, the film thickness deviation occurs because there are few opportunities for density patch formation, but in the sixth embodiment, the film thickness deviation can be suppressed.
For this reason, in the fifth embodiment, electrostatic breakdown occurs at the portion where the film thickness is reduced and development (fogging) occurs in the non-image area. In the sixth embodiment, the film thickness deviation is suppressed. As a result, fogging did not occur.

It should be noted that the configurations and modifications of the respective embodiments (examples) described above can be applied in appropriate combinations within a consistent range. Further, the circumferential dimension of the image carrier 12 of each of the solid patterns PA, PB, PC, and PD is not limited to the above numerical values as long as a necessary amount of toner can be input to the cleaning device. It can be a numerical value.
In each of the above-described embodiments, the maximum writing width, the maximum sheet feeding width, the developing bias voltage, the casing bias voltage, the length in the developing sleeve longitudinal direction (developable area), the developing potential voltage, and the like indicate numerical values of an example. However, it is not limited to those values.
In the fourth and fifth embodiments, the frequency of toner density calibration may be very low depending on the continuous printing conditions. Therefore, when high-accuracy image output is required, it is preferable to use the toner density control performed by detecting the magnetic permeability of the developer as described in the first embodiment.
In the sixth embodiment described above, the toner density calibration is performed every 100 prints. However, if the interval of the number of prints for which the toner density calibration is performed is made too small, the toner density calibration is performed. Therefore, the printing is frequently stopped and the productivity may be lowered. Therefore, it is preferable to set the interval of the number of printed sheets for which the toner density calibration is performed to such an extent that the decrease in productivity does not become remarkable.

  The present invention includes a copier, a printer device, a facsimile device, and a combination of these functions as long as the image forming device includes a cleaning device for cleaning toner remaining on the image carrier and a toner recycling device. The same can be applied to so-called multi-function machines. Further, the present invention can be applied to any of these cases, whether the image forming apparatus has a stand-alone configuration or a network-compatible configuration.

  10: image forming apparatus main body, 12: image carrier, 13: charging device, 14: developing device, 15: transfer / conveying device, 16: cleaning device, 16a: brush roller, 16b: cleaning blade, 17: neutralizing device, 18: Laser writing device, 70: Tray, 81: Operating device, 82: Display device, 83: Auxiliary storage device, 84: Memory device, 85: Main control unit, 86: Image forming unit, 87 Document reading unit, 88: Paper feeding unit, SS, SS ′: reflection density sensor, PA, PB, PC, PD: solid pattern.

Japanese Patent No. 3083000 Japanese Patent No. 3452107 JP 2008-281844 A

Claims (4)

A cleaning device for cleaning the toner remaining on the image carrier for carrying the latent image, and toner recycling for collecting the residual toner scraped from the image carrier by the cleaning device and transporting it again to the developing device An image forming apparatus comprising:
Transfer paper size acquisition means for acquiring the size of the image forming main scanning image direction of the transfer paper used for image formation;
A toner image having a predetermined image pattern is acquired at a predetermined timing at a position corresponding to an end portion in the image forming main scanning direction of the transfer paper used for image formation acquired by the transfer paper size acquisition unit. Control means formed on the top,
An image forming apparatus, wherein the toner image is not transferred onto a transfer sheet, and the toner image is scraped off from the image carrier by the cleaning device. The image forming apparatus according to claim 1,
Density detecting means for detecting the density of the toner image;
An image forming apparatus, further comprising means for adjusting a density of toner used for developing a latent image according to the density detected by the density detecting means. The image forming apparatus according to claim 1, wherein
2. The image forming apparatus according to claim 1, wherein the predetermined timing is when a continuous image forming operation without changing a transfer paper size is completed. The image forming apparatus according to any one of claims 1 to 3,
During continuous image forming operation, when a certain number of image forming operations are completed, the image forming operation is temporarily interrupted, and the transfer paper end corresponding to the transfer paper size in the interrupted image forming operation is An image forming apparatus that forms the toner image at a corresponding position on the image carrier.

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